The present invention is directed to intraluminal devices for stent deployment, percutaneous transluminal coronary angioplasty (PTCA), and the similar procedures that are facilitated by an inflatable tubular member.
PTCA is a widely used procedure for the treatment of coronary heart disease. In this procedure, a balloon dilatation catheter is advanced into the patient""s coronary artery and the balloon on the catheter is inflated within the stenotic region of the patient""s artery to open up the arterial passageway and increase the blood flow through the artery. To facilitate the advancement of the dilatation catheter into the patient""s coronary artery, a guiding catheter having a preshaped distal tip is first percutaneously introduced into the cardiovascular system of a patient by the Seldinger technique through the brachial or femoral arteries. The catheter is advanced therein until the preshaped distal tip of the guiding catheter is disposed within the aorta adjacent the ostium of the desired coronary artery. A balloon dilatation catheter may then be advanced through the guiding catheter into the patient""s coronary artery until the balloon on the catheter is disposed within the stenotic region of the patient""s artery. Once properly positioned across the stenosis, the balloon is inflated one or more times to a predetermined size with radiopaque liquid at relatively high pressures, e.g., generally 4-12 atmospheres (atm), to dilate the stenosed region of a diseased artery. After the inflations, the balloon is finally deflated so that the dilatation catheter can be removed from the dilatated stenosis to resume blood flow.
Similarly, balloon catheters may be used to deploy endoprosthetic devices such as stents. Stents are generally cylindrically shaped intravascular devices that are placed within a damaged artery to hold it open. The device can be used to prevent restenosis and to maintain the patency of blood vessel immediately after intravascular treatments. Typically, a compressed or otherwise small diameter stent is disposed about an expandable member such as a balloon on the distal end of a catheter, and the catheter and stent thereon are advanced through the patient""s vascular system. Inflation of the balloon expands the stent within the blood vessel. Subsequent deflation of the balloon allows the catheter to be withdrawn, leaving the expanded stent within the blood vessel.
One difficulty associated with the use of balloon catheters is the necessity of stocking a wide range of catheters having balloon sizes that range in length as well as diameter. A typical catheter lab stocks catheters with balloon lengths of 15 mm, 20 mm, 30 mm and 40 mm, for example, in a range of diameters such as 1.5 mm to 4.0 mm in 0.25 mm increments. When procedures require different length balloons, different conventional catheters must be used to provide the necessary variety of working lengths. For example, an angioplasty procedure may require the use of two or more stents of different lengths, thus necessitating the use of two of more catheters having balloons of different working lengths to deploy different length stents.
What has been needed is a balloon catheter capable of performing a procedure at a variety of working lengths, which avoids the necessity of using multiple catheters. This invention meets these and other needs.
This invention is directed to a resizable inflatable balloon, having a first dimension that may be resized to a second larger dimension. The balloon generally comprises a first portion having at least a section thereof expandable to a working diameter at a first pressure, and a second portion longitudinally adjacent to the inflatable portion that is not substantially expandable at the first pressure and is expandable to the working diameter at a second pressure greater than the first pressure. To lengthen the balloon working length beyond the length of the first portion, the balloon is resized at the second pressure. Thus, following expansion of the second portion at the second pressure, subsequent inflation of the balloon at the first pressure expands the first portion and the second portion to the working diameter, so that the balloon is thereby resized to the longer working length formed by both the first and second portions being inflated. The second portion may be either proximally or distally adjacent to the first portion.
In a preferred embodiment, the first pressure comprises a working pressure for an angioplasty-type balloon, such as about 10 to about 16, preferably about 14 to about 16 atm, while the second pressure comprises a relatively high pressure, such as about 18 to about 30 atm. The presently preferred materials for the first portion and second portion are polymeric materials that are sufficiently stiff to resist expansion at the first pressure prior to being blown into a balloon, but are not so stiff as to be unexpandable at the second pressure. In one embodiment, the balloon material can be expanded at room temperature to resize the balloon at the second pressure, so that the balloon does not have to be heated during resizing. A variety of polymeric materials used for catheter balloons may be used including polyamides, polyurethanes, and polyesters, provided they have the required expansion characteristics discussed herein. Presently preferred materials include polyurethane block copolymers such as TECOTHANE, copolyesters such as HYTREL, and polyether block amides such as PEBAX. The polyesters such as polyethylene-terephthalate (PET), polyethylene naphthalate (PEN), and polyamides such as nylons which require high pressures greater than about 30 atm to expand at room temperature to form the resized balloon are generally not preferred. However, these materials may be used if the second pressure is greater than about 30 atm or if the materials are processed so as to resize at pressures less than about 30 atm.
The invention also comprises methods for resizing inflatable balloons, including the steps of providing an inflatable balloon comprising a first portion that is expandable to a working diameter at a first pressure, and a second portion adjacent the first portion that is not substantially expandable at the first pressure; placing the inflatable balloon inside a mold; supplying inflation fluid at a second pressure that is greater than the first pressure to expand the second portion to the same working diameter or another (second) working diameter so that subsequent inflation to at least the first pressure expands the first portion and the second portion to the same or the second working diameter. The second working diameter is less than, equal to, or greater than the first working diameter formed at the first pressure, and in a preferred embodiment it is equal or greater than the first diameter. Further, this invention comprises methods for using intraluminal devices having a resizable balloon that typically include the steps of providing an elongated intraluminal device having a resizable balloon adjacent the distal end; guiding the elongated intraluminal device through a patient""s vasculature until the resizable balloon is disposed within a desired region of the patient""s vasculature; supplying inflation fluid at the first pressure to inflate the first portion to the working diameter; withdrawing the elongated intraluminal device; placing the resizable balloon within a mold; supplying inflation fluid at the second pressure to expand the second portion to the same or another working diameter; guiding the elongated intraluminal device through the patient""s vasculature until the resized balloon is disposed within a desired region of the patient""s vasculature; and supplying inflation fluid at the first pressure to expand the first portion and the second portion to the same or the other working diameter. In a presently preferred embodiment, the balloon of the invention is resizable at room temperature, so that the second portion does not require heating before it can be expanded to the working diameter at the second pressure.
This invention provides an inflatable tubular member that is resizable to a variety of working dimensions, so that the desired working dimension for a given procedure or anatomy is readily available. As a result, the catheter of the invention can be safely resized and reduces the number of catheters that must be stocked by catheter laboratories. Other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings.